Knife sharpening apparatus for rotary knives having involute contours



April 26, 1960 H. MILLER 2,933,865 KNIFE SHARPENING APPARATUS FOR ROTARY KNIVES HAVING INVOLUTE CONTOURS Filed 00's. 18, 1957 2 Sheets-Sheet l HENRY MILLER M MM Aprll 26, 1960 H. MILLER 2,933,865

KNIFE SHARFENING APPARATUS FOR ROTARY KNIVES HAVING INVOLUTE CONTOURS Filed Oct. 18, 1957 2 Sheets-Sheet 2 F|G.2 v 34 INVENTOR: HENRY MILLER BY Mzm ATT'Y KNIFE SHARPENING APPARATUS FOR ROTARY KNIVES HAVING INVOLUTE CONTOURS Henry Miller, Chicago, Ill., assignor to The Allhright- Nell Co., Chicago, 111., a corporation of Illinois Application October 18, 1957, Serial No. 690,954

2 Claims. (Cl. 51-249) The present invention relates to sharpening apparatus for rotary knife blades and more particularly to knife sharpening means for slicing machines of the type employing non-circular or involute rotary knives whereby the knives may be sharpened in situ without necessitating removal thereof from the slicing machine. The invention has been illustrated herein as being in the form of an attachment, the same being applied to a slicing machine having a rotary knife provided with an involute shearing edge, such machines commonly being employed for the slicing of bacon or similar food products. The invention is, however, applicable to other types of slicing machines, whether the same be equipped with knives having involute shearing edges or shearing edges which otherwise deviate from the circular. Furthermore, the sharpening apparatus which has been illustrated herein as being in the form of an attachment for-existing slicing machines may, by suitable modification, be designed as original equipment on a slicing machine as manufactured. Irrespective, however, of the particular use to which the present knife sharpening apparatus may be put, the essential features of the invention are at all times preserved.

Where slicing machines having knives with circular shearing edges are concerned, it is merely necessary for knife sharpening purposes to position a sharpening stone in contact with the knife edge at a fixed radial distance from the axis of rotation of the knife. Thus, in a machine of this type, whether the sharpening apparatus be designed as original equipment or as an attachment, no particular problem insofar as causing the sharpening element per se to follow the contour of the knife edge is involved. How

ever, in the case of machines having knives provided with involute shearing edges, the difficulty of causing the sharpening elements per se to follow or track the edge of the rotating blade has necessitated the use of special tracking means, such means usually involving the designing of a cam shaped conformably to the involute curvature of the knife edge, together with a follower carriage carrying the sharpening stone and the movements of which are dependent upon the shape of the cam. Apparatus of this type does not readily lend itself to attachment to and removal from existing slicing machines inasmuch as the overall size and the form of involute curve involved will vary with different machines. Furthermore, the cost of such cam operated equipment materially increases the cost of any individual slicing machine to which it is applied and, as a consequence, most slicing machines having blades of the involute type are not supplied with sharpening equipment so that his necessary, whenever the knife edge becomes dull, to remove the same from the machine for manual sharpening operations. V

The present invention is designed to overcome the above-noted limitations that are attendant upon the construction and operation of sharpening machines having knives provided with involute or other non-circular blades and, toward this end, the invention contemplates the pro- .vision of a sharpening attachment which may readily be applied to existing machines and which have associated therewith a sharpening stone adapted to rest, solely under the influence of gravity, upon the involute shearing edge of the knife, together with means for guiding the sharpening element radially toward and away from the axis of rotation of the knife so that upon turning movement of the knife in either direction, the sharpening element will automatically move radially inwardly or radially outwardly and thus track the knife edge along a linear radial locus developed by the intersection of the rotating knife edge with a radius passing through the sharpening element.

The provision of an apparatus of the character briefly outlined above being among the principal objects of the invention, a further object is to provide such an appara tus which is devoid of springs or similar resilient means for effecting contact between the sharpening element and the moving cutting edge of the knife during sharpening operations.

Another object of the invention is to provide a knife sharpening apparatus of this character which utilizes for the sharpening element thereof an electrically driven or powered rotary sharpening stone, the stone and the electric motor by means of which the latter is driven being mounted upon and movable bodily with a common supporting carriage which is constrained to move in a radial path, the combined gravitational weight of the carriage, the driving motor, the sharpening stone and the driving connection between the motor and stone being applicable to the slicing edge of the knife as the sole application force whereby the knife is pressed against the edge undergoing sharpening in sharpening relationship.

Yet another object of the invention is to provide a sharpening attachment of the character briefly outlined above wherein, after the sharpening stone has been operatively applied to the slicing edge of the knife, selected regions of the slicing edge may, under the manual control of the operator, be brought into register with the sharpening stone as required, thus enabling special treatment to be given to the shearing edge at points where the same is unusually dull for example, or where it is desired that nicks, chips, or other peripheral irregularity be removed from thecutting edge.

Another object of the invention is to provide a knife sharpening attachment for slicing machines having noncircular knives, the attachment including a power driven rotary sharpening stone which, after the attachment has been applied to a given slicing machine, may be adjusted for proper cooperation with the cutting edge of the knife undergoing sharpening.

The provision of a knife sharpening attachment which is relatively simple in its construction and which, therefore, may be manufactured at a comparatively low cost; one which is comprised of a minimum number of moving parts and which, therefore, is unlikely to get out of order; one which is rugged and durable and which, therefore, will withstand rough usage; one which is capable of ease of application to and removal from existing slicing machines; and one which otherwise is well adapted to perform the services required of it, are further desiderata which have been borne in my mind in the production and development of the present invention. 1

Other objects and advantages of the invention, not a this time enumerated, will become more readily apparent as the nature of the invention is better understood.

In the accompanying two sheets of drawings, forminga part of this specification, a preferred embodiment of the invention has been shown.

tachment constructed inaccordance with the principles Patented Apr. 26, 1966 3 of the present invention, and showing the same operatively installed on a slicing machine of the type employing a knife having an involute cutting edge;

Fig. 2 is a front elevation view of the structure shown in Fig. l; I

Fig. 3 is an enlarged detail sectional view taken substantially along the line 33 of Fig. 2; and

Fig. 4 is a fragmentary perspective view of a portion of asharpening stone supporting carriage employed in connection with the present invention and illustrating the manner in which certain carriage adjustments for knife aligning and adjusting purposes may be effected.

Referring now to the drawings in detail, and in particular to Fig. l, a knife sharpening attachment embodying the principles of the present invention is designated in its entirety at and is shown as being operatively applied to a slicing machine 12 of the commercial variety such as is ordinarily employed in the high speed slicing of bacon and similar pro-ducts.

The slicing machine 12 is mounted upon a suitable base 14 and includes a stationary framework 16 providing a table portion 18 presenting a shearing edge 20 and along which table portion the bacon or other product is adapted to be impelled forwardly toward the shearing edge 20. The shearing edge 20 extends across the base portion of a U-shaped frame element 22 secured by clamping screws 24 to the forward face of an upright standard 26 in the form of a casting presenting a flat plate-like portion 28 of generally circular design and which comprises the back plate of the slicing machine. Centered upon and rotatably supported by the back plate 28 of the casing 26 by conventional mounting means as will be described presently is the slicing machine knife 30. The knife 30 is of the involute type and is provided with a peripheral cutting edge 32 which follows the involute path extending from a radially remote point 34 on the knife periphery to a more proximate radial point 36, the two points 34 and 36 lying on a true radius. The knife 30 is formed with a central mounting opening 38 therethrough by means of which the knife may be operatively mounted on a drive shaft 40, the latter being rotatably journalled in the back plate 28 or other portion of the machine framework 16 in any suitable manner and being adapted to be driven by conventional driving means (not shown) in order to cause rotation of the knife 30 in the usual manner of operation of such slicing machines. In order to compensate for the unbalanced gravitational forces inherently present in involute knife structures of the type illustrated herein, a counterweight 42 is mounted on the shaft and this counterweight, together with the knife 30 are adapted to be clamped against a forwardly facing shoulder 44 provided on the shaft 40 by means of a hexagonal nut 46 which is received on a threaded portion 48 of the shaft 40 and which has associated therewith a pair of Washers 50. The arrangement of slicing machine parts thus far described is purely conventional and no claim is made herein to any novelty associated with the same, the novelty of the present invention consisting rather in the novel construction, combination, and arrangement of parts associated with the knife sharpening assembly 10 which will now be more fully described, and subsequently claimed.

The knife sharpening attachment 10 of the present invention involves in its general organization an elongated arm, guide bar or frame-like structure 60 adapted to be clamped to the framework 16 of the slicing machinje 12 in such a manner that the elongated structure extends radially of the knife 30 and in front thereof with its inner end positioned adjacent the axis of rotation of the knife and with its outer end terminating radially'outwardly beyond the overall peripheral extent of the knife, i.e., with the outer end regions of the knife overlapping the pe-- ripheral edge of the knife in any angular position of the latter. The frame-like structure 60 is adapted to extend radially across the front face of the knife 30 at-a prede .cap member 78 of cup-shape design.

termined angle from the horizontal for purposes that will become clear presently, the particular angle selected herein for purposes of illustration being a angle, although it will be understood that other angular positions ofthe frame are contemplated within the scope of the present invention.

The structure or arm 60 includes a generally rectangular open frame piece 62 including parallel side members 64 which are reinforced by web members 66. The outer end of the side members 64 is connected together by a transverse member 68. The inner end of the web pieces 66 is connected by a transverse member 76. The inner end of the side members '64 is secured by means of fastening screws 72 to a bolting flange 74 (see also Figs. 2 and 3) provided on a cylindrical bearing member 76.

The bearing member 76, which is disposed at the inner end of the frame structure 60 is adapted to be fixedly supported in a predetermined position of angular adjustment relative to the slicing machine casing with the bearing member concentric with the axis of rotation of the knife 30. Accordingly, a supporting hub is provided for the bearing member 76, the hub being in the form of a The cap member is provided with an internal socket adapted to be telescopically received over the projecting end of the shaft 40 and fixedly secured to the clamping nut 46. The socket 80 is machined to fit snugly over the face intersections 82 of the nut 46 and a set screw 84 extends radially through an annular flange 86 provided at the rim portion of the cap member 78 and is designed for engagement with a flat face on the nut 46 to firmly anchor the cap member 78 in position over the nut 46 for turning movement in unison therewith. The bearing member 76 is telescopically received over the cap member 78 and a bearing liner 88 is interposed between the cap and bearing member as shown in Fig. 3. A retaining ring 90, secured by screws 92, to the cap member 78, serves, in combination with the flange 86, to confine the bearing member 76 and bearing sleeves 88 in their respective positions on the cap member 76. As will be pointed out subsequently, means are provided for manually applying torque to the assembly including the retaining ring 90, cap member 78 to thereby transmit torque through the nut 46 to the shaft 40 which carries the knife 30 in order that the knife may be moved between desired angular positions thereof for sharpening purposes.

As best seen in Fig. 1, means are provided for anchoring the frame structure 60 in a selected position of angular adjustment relative to the framework 16 whereby the structure 60 may be caused to assume a desired inclination in space. Accordingly, a yoke member is provided with a pair of yoke arms 102 which are anchored as at 164 to the corners of the frame piece 62 and the stern portion 106 of the yoke member 100 is threaded and received thereon a pair of clamping nuts 108 between which there is adapted to be clamped in any desired position of longitudinal adjustment along the stem 106, one end of a clamping bracket 110, the other end of the bracket being provided with a bifurcation 112 adapted to straddle the peripheral edge of the back plate 28 and to be secured thereto by means of clamping studs 114. It will be seen, therefore, that by selecting a particular peripheral region along the generally circular edge of the back plate 28, and aflixing the clamping bracket to this region in the manner briefly described, the angular position of the frame piece 62 relative to the framework 16 may be adjusted.

Referring now to Figs. 1, 2 and 4, the side members 64 of the frame piece 62 constitute guide rails along which there is radially slidable a supporting carriage 116 for a knife sharpening assembly including a rotary sharpening stone 118 and an electric hand tool 120 by means of which the sharpening stone 118 may be power driven, The carriage 116 includes a pair of side frames 122, each having'rotatably mounted thereon spaced pairs of rollers r 124, which atient rollers are adapted to sesame the respective side member 64 of the frame'62. so that the members 122 will be tractionally guided along these frame members. Adjustably supported between the two frame members 122 by means of pin and slot connections 125 is a shelf member 126 which may be in the form of a casting having a sleeve portion 128. Thesleeve portion 128 is adapted to receive therethrough the tubular shank portion 130 of the portable electric hand tool 120. A set screw 132 extendingthrough the sleeve portion 128 serves to clamp the hand tool 120 in any desired position of. axial adjustment within the sleeve 128.

The hand tool 120 is of conventional design, but for purposes of use in connection with the present knife sharpening assembly, 'it'has been modified by disabling the usual trigger switch by means of which the electric motor of the tool is normally energized and deenergized and substituting in its stead a toggle switch 134 which is operatively connected in the motor circuit for the tool. The tool is powered from a suitable source of electric current through lead-in wires which'extend through a suitable conductor cable 135. It will be understood, of course, that the rotary sharpening stone 118 is operatively connected through the tubular shank 128 of the hand tool 120 to the electric motor (not shown) contained withinthe hand tool housing 140 carried on the shank 130 at the end thereof remote'from the rotary sharpening stone 118.

It is to be noted that with the elongatedframe structure 60 clamped in position on the slicing machine framework and with the axis thereof extending at the selected angle of 45 from the horizontal, when the hand tool and sharpening stone assembly is adjusted so that the sharpening stone bears its proper sharpening relationship to the cutting edge of the knife 30, the entire weight of the hand tool and sharpening stone assembly as well as of the carriage on which it is mounted will be proportionately distributed between the inclined surfaces of the frame structure 60 on which the carriage is slidable and the involute cutting edge of the knife 30. The thrust exerted by the sharpening stone against the cutting edge will, of course, be a function of the angle which the frame structure 60 assumes in space, this function being represented by the expression F :W sin 0, where F is the radial thrust exerted against the cutting edge, W is the weight of the carriage and all of the instrumentalities which it supports, and is the deviation angle of the frame structure from a horizontal plane. The smaller the angle relative to the horizontal, the greater will be the weight borne by the inclined surfaces of the frame structure 60 and the less will be the pressure of the stone 118 on the cutting edge of the knife. Conversely, the steeper the angle, the greater will be the downward pressure exerted on this cutting edge.

In order to manually turn the knife 30 about its axis of rotation in the slicing machine, the capmember 78 threadedly receives therein, one end of a torque applying rod 142 which extends in axial alignment with the axis of the knife shaft 40, the other end of the rod carries an operating handle 144 in the form of an elongated generally U-shaped bar, the medial region of which is laterally offset as at 146 from the ends 148 of the bar. The handle 144 has a relative wide radial extent on each side of the shaft 142 so that a high degree of leverage may be applied to the shaft 142 for torque-applying purposes. A lock nut 150 serves to bind the threaded portion of the shaft 142 within the cap member 78 so that the parts will turn in unison. In order to prevent loosening of the nut 46 on the knife shaft 40 during the application of torque to the shaft through the nut 46. from the cap member 78, a drive pin 151 extends through the nut 46 and shaft 40 and may remain in position during normal use of the slicing machine, its removal being required only when it is desired to remove the knife 30 from its assembled position in the slicing machine.

1 In the operation of the'above described knife sharpen.- ing assembly 10 for knife sharpening purposes, several different sharpening procedures will be found effective, these procedures vary according to engineering exigencies as conditions dictate. One method which has been found effective, particularly where the involute curve of the cutting edge of the knife 30 is relatively steep, is for the operatorto manually lift the hand tool and sharpening stone assembly, together with the carriage on which it is mounted, upwardly along the inclined framework structure 60 to such an extent that the sharpening stone 118 will clear the cutting edge in any position of the blade 30. By manipulation of' the handle 144, the outermost point 34 on the involute curve of the cutting edge is then brought into radial register with the sharpening stone 118 and the carriage is released so that, under the influence of gravity, the stone will rest upon the point 34. Thereafter, the handle 144 is slowly turned in a counterclockwise direction as viewed in Fig. 2 so that. the cutting edge of the knife 30 is caused to progressively traverse the sharpening stone 118. During this traversing operation, the stone 118 will ride inwardly on the cutting edge and track the involute curve thereof until such time as it approaches the innermost point 36 on the curve. At this I time, turning operations are terminated and the operator may again lift the entire hand tool and carriage assembly and relocate the stone on the point 34 and repeat the turning operation. Such repetitious sharpening operations are conducted until such time as' the cutting edge is found to be adequately sharpened.

In certain instances, particularly Where the involute curve of the cutting edge of the blade 30 is not steep, it may be found practical to follow the procedure outlined above and, when the innermost point 36 on the curve approaches the sharpening stone 118, the direction of turning movement of the handle 144 may be reversed and the knife blade turned in the opposite direction, i.e., in a clockwise direction so that the sharpening stone will ride outwardly and track the involute curve from the point 36 to the point 34, thus effecting sharpening operations during turning movement of the blade 30 in such opposite direction. In such instances, the operator will not be required to manually lift the carriage 126 and the instrumentalities supported thereby since this carriage will be forced outwardly under the camming action of the involute cutting edge. Precautions must betaken, however, that the operator does not allow the point 34 to completely traverse the sharpening stone 118 in a clockwise direction. Otherwise, release of the carriage by the cutting edge occasioned by the drop-off area or edge of the knife 30 might cause damage to the cutting edge and stone upon impact therebetween.

As previously stated, the angle of the frame structure 60 may be varied by manipulation of the clamping screws 114. In certain instances where light pressures of the sharpening stone 118 on the cutting edge of the knife 30 are adequate to effect the sharpening operations and where the slope of the involute curve of the cutting edge is'relatively steep, sharpening operations involving reversal of the direction of turning movement of the knife blade, thereby eliminating the necessity of resetting the carriage as previously described, may be effected by lessening the slope of the carriage structure 60 relative to the horizontal. In such an instance, more weight will be distributed against the inclined guide rails of the frame strucure 60- and less Weight will be distributed against the cutting edge so that the application of moderate torque to the handle 144 tending to turn the knife blade in a clockwise direction, as viewed in Fig. 2, willnot be unduly resisted by the sharpening stone 118 and the entire sharpening assembly will effectively track the involute curve of the cutting edge of the knife 30 without binding.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without de-; parting from the spirit of the invention. Only insofar as the invention has particularly been pointed out in the accompanying claims is the same to be limited.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

l. The combination with a slicing machine having a stationary framework including a vertical back plate, a knife-supporting shaft mounted for rotation about a horizontal axis in said back plate, a knife having an involute cutting edge carried on said shaft and adapted to be rotated in unison with the shaft in a vertical plane parallel to and spaced forwardly of said back plate, and means including a clamping nut on said shaft forwardly of the knife for securing the knife to said shaft, of a dressing attachment for said machine, said attachment comprising a guide bar extending radially across the front face of the knife and spaced forwardly of the latter, a cap mer'n ber removably secured to said clamping nut, a bearing member on the inner end of said guide bar and cooperat ing with said cap member whereby the bar is mounted for swinging movement about the axis of said shaft, means removably and :adjustably securing the distal end of the guide bar to the peripheral regions of said back plate for circumferential adjustment whereby the inclination of said guide bar may be varied, a supporting carriage freely slidable on said guide bar for radial movements relative to the axis of rotation of the knife, a dressing tool assembly of the hand tool variety including a casing, an electric motor within the casing, and a rotary dressing tool element operatively connected to the motor in driving relation, means adjustably mounting said motor casing on said carriage whereby the dressing tool element may be positioned over said cutting edge of the knife and caused to rest thereon under the influence of gravitational forces acting on the dressing tool assembly, and an operating handle secured to said cap member for applying turning movements to the latter and consequently to said knife whereby, upon movement of the latter, said dressing tool element will track the path of movement of said involute cutting edge.

2. The combination with a slicing machine having a stationary framework, a knife-supporting shaft mounted for rotation about a horizontal axis in said framework,

"a knife having an involute cutting edge carried on said shaft and adaptedto be rotated in unison with theshaft in a vertical plane, and means including a clamping nut on said shaft forwardly of the knife for securing the knife to the shaft, of a dressing attachment for said machine, said attachment comprising a guide bar extendirig radially across the front face of the knife and spaced forwardly of the latter, a cap member removably secured to said clamping nut, a bearing member on the inner end of said guide bar and cooperating with said cap member whereby the bar is mounted for swinging movement about the axis of said shaft, means for releasably clamping the distal end of the guide bar to selected points on the framework to vary the inclination of the guide bar, a supporting carriage freely slidable on said guide bar for radial movements relative to the axis of rotationiof the knife, a dressing tool assembly including a rotary'dressing tool-and an electric motor for driving the tool adjustably mounted on said carriage whereby the dressing tool may be positioned over the cutting edge of the knife and caused to rest thereon under the influence of gravity, and an operating handle secured to said cap member for applying turning movements to the latter and consequently to the knife whereby, upon movement of the latter, said dressing tool will track the path of movement of said involute cutting edge,

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